Okay, only works with old bulbs and its a trick-question not a puzzle

#1

Comment body goes here.

#2

I agree with you.
Ideally, if we are allowed to switch on 2 bulbs at a time then, turn any two switches on and check, then come down and turn one of the switch OFF, so 2 rounds
If only 1 switch can be turned ON at a time, even then 2 rounds, as we mark which bulb and switch was never turned ON!

If it’s puzzle, and you can’t physically access bulbs then answer is 2. else 1.

#3

Well, the puzzle itself is very old.

#4

Put irons in place of bulbs. Answer is 2.